Visible and infrared intensity limiter

Abstract

The laser light is polarized and sent through an electro-optic pockels cellhere it is phased shifted in a duty cycle in accordance with the amplitude intensity. The light is then sent through an analyzer which will act as an attenuator to regulate the final amplitude output of the light.

We claim: 
     
       1. A system for controlling the amplitude of laser light from a laser comprising: a polarizer for polarizing said light in a predetermined direction; an electro-optic pockels cell having a control input terminal; an analyzer being polarized such that it will pass electromagnetic energy polarized in said predetermined direction and will cut off electromagnetic energy polarized 90° to said predetermined direction; said polarizer, cell and analyzer being positioned such that the light will pass through said polarizer, cell and analyzer in that order; a partial reflector being positioned to reflect a portion of the light output passing through said analyzer; a germanium detector positioned to receive light reflected from said reflector; said detector having an output terminal which will have a signal thereon which is representative of the amplitude level of said laser light; a high gain switchable amplifier connected to the output terminal of said detector so as to provide a control signal when said laser light reaches a preselected intensity amplitude level; said high gain switchable amplifier produces a control signal only when said detector measures an amplitude level greater than said preselected level; a high frequency filter connected between the amplifier and the control input of said pockels cell; and the control signal being connected through the filter to the control input terminal of said cell so as to cause the cell to rotate the polarization of said electromagnetic energy 90° with respect to said predetermined direction.